The increasing demand for low cost, miniaturized, power efficient communication systems is driving the requirement for higher levels of functionality to be incorporated within integrated circuits. To minimize the area and associated costs of these integrated circuits, novel and innovative means of providing low noise amplification in environments which may have high levels of interference is highly desirable. However, such benefits should not be obtained at the cost reducing performance requirements, such as, for example, linearity and/or power consumption. Maintaining existing performance requirements is important because emerging communication standards have rigorous receiver desensitization requirements and receiver power consumption must be minimized to maintain a competitive advantage.
Once class of low noise amplifiers includes a Low Noise Transconductance Amplifier (LNTA), which generally behaves as a voltage controlled current source (i.e., provides an output current based upon an input voltage signal). Conventional LNTA designs have partitioned their functions into two blocks; an LNA (Low Noise Amplification) block followed by a TA (Transconductance Amplification) block. This partitioning allows designers to reuse existing LNA intellectual property but may result in a suboptimum design that can use greater power and die area with reduced linearity and thus immunity from interfering signals. The conventionally partitioned LNTA design may be fundamentally limited by the LNA stage that must provide considerable voltage gain to obtain adequate transconductance from the LNA/TA combination. Moreover, the LNA may also utilize an inductive load to resonate out the parasitic capacitance of the TA stage. Inductors may further increase cost as they can take up a significant amount of die area on an integrated circuit, and may require additional tuning steps for proper operation. Moreover, conventional LNTA designs may duplicate amplifier circuitry in order to provide both in-phase and quadrature output signals, thus further increasing the size requirements on the integrated circuit.
Accordingly, there is a need for a single stage LNTA they can provide considerable savings in power and die area, along with improved linearity and operating bandwidth.